Acidic multimetallic catalytic composite

ABSTRACT

An acidic multimetallic catalytic composite especially useful for converting hydrocarbons comprises a combination of catalytically effective amounts of a platinum group component, a nickel component, a uranium component, and a halogen component with a porous carrier material. The platinum group, uranium, nickel, and halogen components are present in the multimetallic catalyst in amounts respectively, calculated on an elemental basis, corresponding to about 0.01 to about 2 wt. % platinum group metal, about 0.1 to about 10 wt. % uranium, about 0.05 to about 5 wt. % nickel, and about 0.1 to about 3.5 wt. % halogen. Moreover, these metallic components are uniformly dispersed throughout the porous carrier material in carefully controlled oxidation states such that substantially all of the platinum group component is present therein in the elemental metallic state, substantially all of the catalytically available nickel component is present in the elemental metallic state or in a state which is reducible to the elemental metallic state under hydrocarbon conversion conditions, or in a mixture of these states, while substantially all of the uranium component is present in an oxidation state above that of the elemental metal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of our prior, copending application Ser.No. 928,650 filed July 27, 1978 and now U.S. Pat. No. 4,179,360. All ofthe teachings of this prior application are specifically incorporatedherein by reference.

The subject of the present invention is a novel acidic multimetalliccatalytic composite which has exceptional activity and resistance todeactivation when employed in a hydrocarbon conversion process thatrequires a catalyst having both a hydrogenation-dehydrogenation functionand a carbonium ion-forming function. More precisely, the presentinvention involves a novel dual-function acidic multimetallic catalyticcomposite which, quite surprisingly, enables substantial improvements inhydrocarbon conversion processes that have traditionally used adual-function catalyst. In another aspect, the present inventioncomprehends the improved processes that are produced by the use of acatalytic composite comprising a combination of catalytically effectiveamounts of a platinum group component, a nickel component, a uraniumcomponent, and a halogen component with a porous carrier material;specifically, an improved reforming process which utilizes the subjectcatalyst to improve activity, selectivity, and stabilitycharacteristics.

Composites having a hydrogenation-dehydrogenation function and acarbonium ion-forming function are widely used today as catalysts inmany industries, such as the petroleum and petrochemical industry, toaccelerate a wide spectrum of hydrocarbon conversion reactions.Generally, the carbonium ion-forming function is thought to beassociated with an acid-acting material of the porous, adsorptive,refractory oxide type which is typically utilized as the support orcarrier for a heavy metal component such as the metals or compounds ofmetals of Groups V through VIII of the Periodic Table to which aregenerally attributed the hydrogenation-dehydrogenation function.

These catalytic composites are used to accelerate a wide variety ofhydrocarbon conversion reactions such as hydrocracking, hydrogenolysis,isomerization, dehydrogenation, hydrogenation, desulfurization,cyclization, polymerization, alkylation, cracking, hydroisomerization,dealkylation, transalkylation, etc. In many cases, the commercialapplications of these catalysts are in processes where more than one ofthe reactions are proceeding simultaneously. An example of this type ofprocess is reforming wherein a hydrocarbon feedstream containingparaffins and naphthenes is subjected to conditions which promotedehydrogenation of naphthenes to aromatics, dehydrocyclization ofparaffins to aromatics, isomerization of paraffins and naphthenes,hydrocracking and hydrogenolysis of naphthenes and paraffins, and thelike reactions, to produce an octane-rich or aromatic-rich productstream. Another example is a hydrocracking process wherein catalysts ofthis type are utilized to effect selective hydrogenation and cracking ofhigh molecular weight unsaturated materials, selective hydrocracking ofhigh molecular weight materials, and other like reactions, to produce agenerally lower boiling, more valuable output stream. Yet anotherexample is a hydroisomerization process wherein a hydrocarbon fractionwhich is relatively rich in straight-chain paraffin compounds iscontacted with a dual-function catalyst to produce an output stream richin isoparaffin compounds.

Regardless of the reaction involved or the particular process involved,it is of critical importance that the dual-function catalyst exhibit notonly the capability to initially perform its specified functions, butalso that it has the capability to perform them satisfactorily forprolonged periods of time. The analytical terms used in the art tomeasure how well a particular catalyst performs its intended functionsin a particular hydrocarbon reaction environment are activity,selectivity, and stability. And for purposes of discussion here, theseterms are conveniently defined for a given charge stock as follows: (1)activity is a measure of the catalyst's ability to convert hydrocarbonreactants into products at a specified severity level where severitylevel means the conditions used--that is, the temperature, pressure,contact time, and pressure of diluents such as H₂ ; (2) selectivityrefers to the amount of desired product or products obtained relative tothe amount of reactants charged or converted; (3) stability refers tothe rate of change with time of the activity and selectivityparameters--obviously, the smaller rate implying the more stablecatalyst. In a reforming process, for example, activity commonly refersto the amount of conversion that takes place for a given charge stock ata specified severity level and is typically measured by octane number ofthe C₅ + product stream; selectivity refers to the amount of C₅ + yield,relative to the amount of the charge, that is obtained at the particularactivity or severity level; and stability is typically equated to therate of change with time of activity, as measured by octane number ofC₅ + product, and of selectivity as measured by C₅ + yield. Actually,the last statement is not strictly correct because generally acontinuous reforming process is run to produce a constant octane C₅ +product with severity level being continuously adjusted to attain thisresult; and furthermore, the severity level is for this process usuallyvaried by adjusting the conversion temperature in the reaction so that,in point of fact, the rate of change of activity finds response in therate of change of conversion temperature and changes in this lastparameter are customarily taken as indicative of activity stability.

As is well known to those skilled in the art, the principal cause ofobserved deactivation or instability of a dual-function catalyst when itis used in a hydrocarbon conversion reaction is associated with the factthat coke forms on the surface of the catalyst during the course of thereaction. More specifically, in these hydrocarbon conversion processes,the conditions utilized typically result in the formation of heavy, highmolecular weight, black, solid or semi-solid, carbonaceous materialwhich is a hydrogen-deficient polymeric substance having properties akinto both polynuclear aromatics and graphite. This material coats thesurface of the catalyst and thus reduces its activity by shielding itsactive sites from the reactants. In other words, the performance of thisdual-function catalyst is sensitive to the presence of carbonaceousdeposits or coke on the surface of the catalyst. Accordingly, the majorproblem facing workers in this area of the art is the development ofmore active and/or selective catalytic composites that are not assensitive to the presence of these carbonaceous materials and/or havethe capability to suppress the rate of the formation of thesecarbonaceous materials on the catalyst. Viewed in terms of performanceparameters, the problem is to develop a dual-function catalyst havingsuperior activity, selectivity, and stability characteristics. Inparticular, for a reforming process the problem is typically expressedin terms of shifting and stabilizing the C₅ + yield-octane relationshipat the lowest possible severity level--C₅ + yield being representativeof selectivity and octane being proportional to activity.

We have now found a dual-function acidic multimetallic catalyticcomposite which possesses improved activity, selectivity, and stabilitycharacteristics when it is employed in a process for the conversion ofhydrocarbons of the type which have heretofore utilized dual-functionacidic catalytic composites such as processes for isomerization,hydroisomerization, dehydrogenation, desulfurization, denitrogenization,hydrogenation, alkylation, dealkylation, disproportionation,polymerization, hydrodealkylation, transalkylation, cyclization,dehydrocyclization, cracking, hydrocracking, halogenation, reforming,and the like processes. In particular, we have ascertained that anacidic catalyst, comprising a combination of catalytically effectiveamounts of a platinum group component, a nickel component, a uraniumcomponent, and a halogen component with a porous refractory carriermaterial, can enable the performance of hydrocarbon conversion processesutilizing dual-function catalysts to be substantially improved if themetallic components are uniformly dispersed throughout the carriermaterial and if their oxidation states are controlled to be in thestates hereinafter specified. Moreover, we have determined that anacidic catalytic composite, comprising a combination of catalyticallyeffective amounts of a platinum group component, a nickel component, auranium component, and a chloride component with an alumina carriermaterial, can be utilized to substantially improve the performance of areforming process which operates on a low-octane gasoline fraction toproduce a high-octane reformate if the metallic components are uniformlydispersed throughout the alumina carrier material, if the catalyst isprepared and maintained during use in the process in a substantiallysulfur-free state, and if the oxidation states of the metalliccomponents are fixed in the state hereinafter specified. In the case ofa reforming process, the principal advantage associated with the use ofthe present invention involves the acquisition of the capability tooperate in a stable manner in a high severity operation; for example, alow or moderate pressure reforming process designed to produce a C₅ +reformate having an octane of about 100 F-1 clear. As indicated, thepresent invention essentially involves the finding that the addition ofa combination of a uranium component and a nickel component to adual-function acidic hydrocarbon conversion catalyst containing aplatinum group component can enable the performance characteristics ofthe catalyst to be sharply and materially improved, if the hereinafterspecified limitations on amounts of ingredients, exclusion of sulfur,oxidation states of metal, and distribution of metallic components inthe support are met.

It is, accordingly, one object of the present invention to provide anacidic multimetallic hydrocarbon conversion catalyst having superiorperformance characteristics when utilized in a hydrocarbon conversionprocess. A second object is to provide an acidic multimetallic catalysthaving dual-function hydrocarbon conversion performance characteristicsthat are relatively insensitive to the deposition of hydrocarbonaceousmaterial thereon. A third object is to provide preferred methods ofpreparation of this acidic multimetallic catalytic composite whichinsures the achievement and maintenance of its properties. Anotherobject is to provide an improved reforming catalyst having superioractivity, selectivity, and stability characteristics. Yet another objectis to provide a dual-function hydrocarbon conversion catalyst whichutilizes a combination of a uranium component and a nickel component tobeneficially interact with and promote an acidic catalyst containing aplatinum group component.

In brief summary, the present invention is, in one embodiment, an acidiccatalytic composite comprising a porous carrier material containing, onan elemental basis, about 0.01 to about 2 wt. % platinum group metal,about 0.05 to about 5 wt. % nickel, about 0.1 to about 10 wt. % uranium,and about 0.1 to about 3.5 wt. % halogen. The platinum group, uranium,and catalytically available nickel components are, moreover, uniformlydispersed throughout the porous carrier material and the oxidationstates of the metals are adjusted so that (1) substantially all of theplatinum group component is present in the elemental metallic state, (2)substantially all of the uranium component is present in an oxidationstate above that of the elemental metal, and (3) substantially all ofthe catalytically available nickel component is present in the elementalmetallic state or in a state which is reducible to the elementalmetallic state under hydrocarbon conversion conditions or in a mixtureof these states.

A second embodiment relates to an acidic substantially sulfur-freecatalytic composite comprising a porous carrier material containing, onan elemental basis, about 0.05 to about 1 wt. % platinum group metal,about 0.1 to about 2.5 wt. % nickel, about 0.25 to about 5 wt. %uranium, and about 0.5 to about 1.5 wt. % halogen. The platinum group,uranium, and catalytically available nickel components are uniformlydispersed throughout the porous carrier material of this component suchthat substantially all of the platinum group component is present in thecorresponding elemental metallic state, substantially all of the uraniumcomponent is present in an oxidation state above that of the elementalmetal, and substantially all of the catalytically available nickelcomponent is present in the elemental metallic state or in a state whichis reducible to the elemental metallic state under hydrocarbonconversion conditions or in a mixture of these states.

A third embodiment relates to the catalytic composite described in thefirst or second embodiment wherein the halogen component is combinedchloride.

Yet another embodiment involves a process for the conversion of ahydrocarbon comprising contacting the hydrocarbon and hydrogen with thecatalytic composite described above in the first or second or thirdembodiment at hydrocarbon conversion conditions.

A preferred embodiment comprehends a process for reforming a gasolinefraction which comprises contacting the gasoline fraction and hydrogenwith the catalytic composite described above in the first or second orthird embodiment at reforming conditions selected to produce a highoctane reformate.

A highly preferred embodiment is a process for reforming a gasolinefraction which comprises contacting the gasoline fraction and hydrogenin a substantially water-free and sulfur-free environment with thecatalytic composite characterized in the first, second, or thirdembodiment at reforming conditions selected to produce a high octanereformate.

Other objects and embodiments of the present invention relate toadditional details regarding preferred catalytic ingredients, preferredamounts of ingredients, suitable methods of composite preparation,operating conditions for use in the hydrocarbon conversion processes,and the like particulars, which are hereinafter given in the followingdetailed discussion of each of these facets of the present invention.

The acidic multimetallic catalyst of the present invention comprises aporous carrier material or support having combined therewithcatalytically effective amounts of a platinum group component, a nickelcomponent, a uranium component, and a halogen component.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon conversion process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as: (1) activated carbon, coke, orcharcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated, for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc., (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide,cesium oxide, hafnium oxide, zinc oxide, magnesia boria, thoria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, MnAl₂ O₄, CaAl₂ O₄, and other like compounds having theformula MO.Al₂ O₃ where M is a metal having a valence of 2; and (7)combinations of elements from one or more of these groups. The preferredporous carrier materials for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas gamma-, eta-, and theta-alumina, with gamma- or eta-alumina givingbest results. In addition, in some embodiments the alumina carriermaterial may contain minor proportions of other well known refractoryinorganic oxides such as silica, zirconia, magnesia, etc.; however, thepreferred support is substantially pure gamma- or eta-alumina. Preferredcarrier materials have an apparent bulk density of about 0.3 to about0.8 g/cc and surface area characteristics such that the average porediameter is about 20 to 300 Angstroms, the pore volume is about 0.1 toabout 1 cc/g and the surface area is about 100 to about 500 m² /g. Ingeneral, best results are typically obtained with a gamma-aluminacarrier material which is used in the form of spherical particleshaving: a relatively small diameter (i.e. typically about 1/16 inch), anapparent bulk density of about 0.3 to about 0.8 g/cc, a pore volume ofabout 0.4 ml/g, and a surface area of about 150 to about 250 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere; and alumina spheres may becontinuously manufactured by the well-known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

Another particularly preferred alumina carrier material is synthesizedfrom a unique crystalline alumina powder which has been characterized inU.S. Pat. Nos. 3,852,190 and 4,012,313 as a byproduct from a Zieglerhigher alcohol synthesis reaction as described in Ziegler's U.S. Pat.No. 2,892,858. For purposes of simplification, the name "Ziegleralumina" is used herein to identify this material. It is presentlyavailable from the Conoco Chemical Division of Continental Oil Companyunder the trademark Catapal. This material is an extremely high purityalpha-alumina monohydrate (boehmite) which after calcination at a hightemperature has been shown to yield a high purity gamma-alumina. It iscommercially available in three forms: (1) Catapal SB--a spray driedpowder having a typical surface area of 250 m² /g; (2) Catapal NG--arotary kiln dried alumina having a typical surface area of 180 m² /g;and (3) Dispal M--a finely divided dispersable product having a typicalsurface area of about 185 m² /g. For purposes of the present invention,the preferred starting material is the spray dried powder, Catapal SB.This alpha-alumina monohydrate powder may be formed into a suitablecatalyst material according to any of the techniques known to thoseskilled in the catalyst carrier material forming art. Spherical carriermaterial particles can be formed, for example, from this Ziegler aluminaby: (1) converting the alpha-alumina monohydrate powder into an aluminasol by reaction with a suitable peptizing acid and water and thereafterdropping a mixture of the resulting sol and a gelling agent into an oilbath to form spherical particles of an alumina gel which are easilyconverted to a gamma-alumina carrier material by known methods; (2)forming an extrudate from the powder by established methods andthereafter rolling the extrudate particles on a spinning disc untilspherical particles are formed which can then be dried and calcined toform the desired particles of spherical carrier material; and (3)wetting the powder with a suitable peptizing agent and thereafterrolling particles of the powder into spherical masses of the desiredsize in much the same way that children have been known to make parts ofsnowmen by rolling snowballs down hills covered with wet snow. Thisalumina powder can also be formed in any other desired shape or type ofcarrier material known to those skilled in the art such as rods, pills,pellets, tablets, granules, extrudates and the like forms by methodswell known to the practitioners of the catalyst carrier material formingart. The preferred type of carrier material for the present invention isa cylindrical extrudate having a diameter of about 1/32" to about 1/8"(especially about 1/16") and a length to diameter (L/D) ratio of about1:1 to about 5:1, with a L/D ratio of about 2:1 being especiallypreferred. The especially preferred extrudate form of the carriermaterial is preferably prepared by mixing the alumina powder with waterand a suitable peptizing agent such as nitric acid, acetic acid,aluminum nitrate and the like material until an extrudable dough isformed. The amount of water added to form the dough is typicallysufficient to give a loss on ignition (LOI) at 500° C. of about 45 to 65wt. %, with a value of about 55 wt. % being especially preferred. On theother hand, the acid addition rate is generally sufficient to provideabout 2 to 7 wt. % of the volatile free alumina powder used in the mix,with a value of about 3 to 4% being especially preferred. The resultingdough is then extruded through a suitably sized die to form extrudateparticles. These particles are then dried at a temperature of about 500°to 800° F. for a period of about 0.1 to about 5 hours and thereaftercalcined at a temperature of about 900° F. to about 1500° F. for aperiod of about 0.5 to about 5 hours to form the preferred extrudateparticles of the Ziegler alumina carrier material. In addition, in someembodiments of the present invention the Ziegler alumina carriermaterial may contain minor proportions of other well known refractoryinorganic oxides such as silica, titanium dioxide, zirconium dioxide,chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafniumoxide, zinc oxide, iron oxide, cobalt oxide, magnesia, boria, thoria,and the like materials which can be blended into the extrudable doughprior to the extrusion of same. In the same manner crystalline zeoliticaluminosilicates such as naturally occurring or synthetically preparedmordenite and/or faujasite, either in the hydrogen form or in a formwhich has been treated with a multivalent cation, such as a rare earth,can be incorporated into this carrier material by blending finelydivided particles of same into the extrudable dough prior to extrusionof same. A preferred carrier material of this type is substantially pureZiegler alumina having an apparent bulk density (ABD) of about 0.6 to 1g/cc (especially an ABD of about 0.7 to about 0.85 g/cc), a surface areaof about 150 to about 280 m² /g (preferably about 185 to about 235 m²/g), and a pore volume of about 0.3 to about 0.8 cc/g.

The expression "catalytically available nickel" as used herein isintended to mean the portion of the nickel component that is availablefor use in accelerating the particular hydrocarbon conversion reactionof interest. For certain types of carrier materials which can be used inthe preparation of the instant catalyst composite, it has been observedthat a portion of the nickel incorporated therein is essentiallybound-up in the crystal structure thereof in a manner which essentiallymakes it more a part of the refractory carrier material than acatalytically active component. Specific examples of this effect areobserved when the carrier material can form a refractory spinel orspinel-like structure with a portion of the nickel component and/or whena refractory nickel oxide or aluminate is formed by reaction of thecarrier material (or precursor thereof) with a portion of the nickelcomponent. When this effect occurs, it is only with great difficultythat the portion of the nickel bound-up with the support can be reducedto a catalytically active state and the conditions required to do thisare beyond the severity levels normally associated with hydrocarbonconversion conditions and are in fact likely to seriously damage thenecessary porous characteristics of the support. In the cases wherenickel can interact with the crystal structure of the support to rendera portion thereof catalytically unavailable, the concept of the presentinvention merely requires that the amount of nickel added to the subjectcatalyst be adjusted to satisfy the requirements of the support as wellas the catalytically available nickel requirements of the presentinvention. Against this background then, the hereinafter statedspecifications for oxidation state and dispersion of the nickelcomponent are to be interpreted as directed to a description of thecatalytically available nickel. On the other hand, the specificationsfor the amount of nickel used are to be interpreted to include all ofthe nickel contained in the catalyst in any form.

One essential constituent of the acidic multimetallic catalyst of thepresent invention is a uranium component. This component may in generalbe present in the instant catalytic composite in any catalyticallyavailable form wherein substantially all of the uranium moiety ispresent in a positive oxidation state such as a compound like the oxide,hydroxide, halide, oxyhalide, aluminate, or in chemical combination withone or more of the other ingredients of the catalyst. It is believedthat best results are obtained when substantially all of the uraniumcomponent is present in the composite in the form of uranium oxide andthe subsequently described oxidation and reduction steps that arepreferably used in the preparation of the instant catalytic compositeare specifically designed to achieve this end. This uranium componentcan be used in any amount which is catalytically effective, with goodresults obtained, on an elemental basis, with about 0.1 to about 10 wt.% uranium in the catalyst. Best results are ordinarily achieved withabout 0.25 to about 5 wt. % uranium, calculated on an elemental basis.

This uranium component may be incorporated in the catalytic composite inany suitable manner known to the art to result in a relatively uniformdispersion of the uranium moiety in the carrier material, ion exchangewith the gelled carrier material, or impregnation with the carriermaterial either after, before, or during the period when it is dried andcalcined. It is to be noted that it is intended to include within thescope of the present invention all conventional methods forincorporating and simultaneously uniformly distributing a metalliccomponent in a catalytic composite and the particular method ofincorporation used is not deemed to be an essential feature of thepresent invention. One preferred method of incorporating the uraniumcomponent into the catalytic composite involves cogelling orcoprecipitating the uranium component in the form of the correspondinghydrous oxide during the preparation of the preferred carrier material,alumina. This method typically involves the addition of a suitablesol-soluble uranium compound such as uranyl acetate, uranyl chloride,uranyl nitrate, and the like to the alumina hydrosol and then combiningthe hydrosol with a suitable gelling agent and dropping the resultingmixture into an oil bath, etc., as explained in detail hereinbefore.Alternatively, the uranium compound can be added to the gelling agent.After drying and calcining the resulting gelled carrier material in air,there is obtained an intimate combination of alumina and uranium oxide,or uranium aluminate or uranium oxyhalide. An especially preferredmethod of incorporating the uranium component into the catalyticcomposite involves utilization of a soluble, decomposable compound ofuranium to impregnate the porous carrier material. In general, thesolvent used in this impregnation step is selected on the basis of thecapability to dissolve the desired uranium compound without adverselyaffecting the carrier material or the other ingredients of thecatalyst--for example, a suitable alcohol, ether, acid and the likesolvents. The solvent is preferably an aqueous, acidic solution. Thus,the uranium component may be added to the carrier material bycommingling the latter with an aqueous acidic solution of suitableuranium salt, complex, or compound such as uranium tetrabromide, uraniumtribromide, uranium tetrachloride, uranium trichloride, uraniumtetrafluoride, uranyl acetate, uranyl chloride, uranyl formate, uranylnitrate, uranyl oxalate, uranyl carbonate and the like compounds. Aparticularly preferred impregnation solution comprises an acidic aqueoussolution of uranyl acetate. Suitable acids for use in the impregnationsolution are: inorganic acids such as hydrochloric acid, nitric acid,and the like, and strongly acidic organic acids such as oxalic acid,malonic acid, citric acid, and the like. In general, the uraniumcomponent can be impregnated either prior to, simultaneously with, orafter the other ingredients are added to the carrier material. However,excellent results are obtained when the uranium component is impregnatedsimultaneously with the platinum group and nickel components. In fact, apreferred impregnation solution is an aqueous solution of chloroplatinicacid, hydrochloric acid, uranyl acetate, and nickel chloride.

A second essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum,iridium, osmium, ruthenium, rhodium, palladium, or mixtures thereof, asa second component of the present composite. It is an essential featureof the present invention that substantially all of this platinum groupcomponent exists within the final catalytic composite in the elementalmetallic state. Generally, the amount of this component present in thefinal catalytic composite is small compared to the quantities of theother components combined therewith. In fact, the platinum groupcomponent generally will comprise about 0.01 to about 2 wt. % of thefinal catalytic composite, calculated on an elemental basis. Excellentresults are obtained when the catalyst contains about 0.05 to about 1wt. % of platinum, iridium, rhodium, or palladium metal. Particularlypreferred mixtures of these metals are platinum and iridium, andplatinum and rhodium.

This platinum group component may be incorporated in the catalyticcomposite in any suitable manner known to result in a relatively uniformdistribution of this component in the carrier material such ascoprecipitation or cogelation, ion exchange or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum group metal to impregnate thecarrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloroiridic or chloropalladicacid. Other water-soluble compounds or complexes of platinum groupmetals may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, hexamminerhodium chloride,rhodium carbonylchloride, rhodium trichloride hydrate, rhodium nitrate,sodium hexachlororhodate (III), sodium hexanitrorhodate (III), iridiumtribromide, iridium dichloride, iridium tetrachloride, sodiumhexanitroiridate (III), potassium or sodium chloroiridate, potassiumrhodium oxalate, etc. The utilization of a platinum, iridium, rhodium,or palladium chloride compound, such as chloroplatinic, chloroiridic, orchloropalladic acid or rhodium trichloride hydrate, is preferred sinceit facilitates the incorporation of both the platinum group componentsand at least a minor quantity of the halogen component in a single step.Hydrogen chloride or the like acid is also generally added to theimpregnation solution in order to further facilitate the incorporationof the halogen component and the uniform distribution of the metalliccomponents throughout the carrier material. In addition, it is generallypreferred to impregnate the carrier material after it has been calcinedin order to minimize the risk of washing away the valuable platinum orpalladium compounds; however, in some cases it may be advantageous toimpregnate the carrier material when it is in a gelled state.

A third essential ingredient of the acidic multimetallic catalyticcomposite of the present invention is a nickel component. Although thiscomponent may be initially incorporated into the composite in manydifferent decomposable forms which are hereinafter stated, my basicfinding is that the catalytically active state for hydrocarbonconversion with this component is the elemental metallic state.Consequently, it is a feature of my invention that substantially all ofthe catalytically available nickel component exists in the catalyticcomposite either in the elemental metallic state or in a state which isreducible to the elemental state under hydrocarbon conversion conditionsor in a mixture of these states. Examples of this reducible state areobtained when the catalytically available nickel component is initiallypresent in the form of nickel oxide, halide, hydroxide, oxyhalide, andthe like reducible compounds. As a corollary to this basic finding onthe active state of the catalytically available nickel component, itfollows that the presence of catalytically available nickel in formswhich are not reducible at hydrocarbon conversion conditions is to bescrupulously avoided if the full benefits of the present invention areto be realized. Illustrative of these undesired forms are nickel sulfideand the nickel oxysulfur compounds such as nickel sulfate. Best resultsare obtained when the composite initially contains all of thecatalytically available nickel component in the elemental metallic stateor in a reducible oxide state or in a mixture of these states. Allavailable evidence indicates that the preferred preparation procedurespecifically described in Example I results in a catalyst having thecatalytically available nickel component in the elemental metallic stateor in a reducible oxide form. The nickel component may be utilized inthe composite in any amount which is catalytically effective, with thepreferred amount being about 0.05 to about 5 wt. % thereof, calculatedon an elemental nickel basis. Typically, best results are obtained withabout 0.1 to about 2.5 wt. % nickel. It is, additionally, preferred toselect the specific amount of nickel from within this broad weight rangeas a function of the amount of the platinum group component, on anatomic basis, as is explained hereinafter.

The nickel component may be incorporated into the catalytic composite inany suitable manner known to those skilled in the catalyst formulationart to result in a relatively uniform distribution of the catalyticallyavailable nickel in the carrier material such as coprecipitation,cogelation, ion exchange, impregnation, etc. In addition, it may beadded at any stage of the preparation of the composite--either duringpreparation of the carrier material or thereafter--since the precisemethod of incorporation used is not deemed to be critical. However, bestresults are obtained when the catalytically available nickel componentis relatively uniformly distributed throughout the carrier material in arelatively small particle or crystallite size, and the preferredprocedures are the ones that are known to result in a composite having arelatively uniform distribution of the catalytically available nickelmoiety in a relatively small particle size. One acceptable procedure forincorporating this component into the composite involves cogelling orcoprecipitating the nickel component during the preparation of thepreferred carrier material, alumina. This procedure usually comprehendsthe addition of a soluble, decomposable, and reducible compound ofnickel such as nickel chloride or nitrate to the alumina hydrosol beforeit is gelled. The resulting mixture is then finished by conventionalgelling, aging, drying, and calcination steps as explained hereinbefore.One preferred way of incorporating this component is an impregnationstep wherein the porous carrier material is impregnated with a suitablenickel-containing solution either before, during, or after the carriermaterial is calcined or oxidized. The solvent used to form theimpregnation solution may be water, alcohol, ether, or any othersuitable organic or inorganic solvent provided the solvent does notadversely interact with any of the other ingredients of the composite orinterfere with the distribution and reduction of the nickel component.Preferred impregnation solutions are aqueous solutions of water-soluble,decomposable, and reducible nickel compounds or complexes such as nickelbromate, nickel bromide, nickel perchlorate, nickel chloride, nickelfluoride, nickel iodide, nickel nitrate, hexamminenickel (II) chloride,diaquotetramminenickel (II) nitrate, hexamminenickel (II) nitrate, andthe like compounds or complexes. Best results are ordinarily obtainedwhen the impregnation solution is an aqueous acidic solution of nickelchloride or nickel nitrate. This nickel component can be added to thecarrier material, either prior to, simultaneously with, or after theother metallic components are combined therewith. Best results areusually achieved when this component is added simultaneously with theplatinum group and uranium components via an acidic aqueous impregnationsolution.

It is essential to incorporate a halogen component into the acidicmultimetallic catalytic composite of the present invention. Although theprecise form of the chemistry of the association of the halogencomponent with the carrier material is not entirely known, it iscustomary in the art to refer to the halogen component as being combinedwith the carrier material, or with the other ingredients of the catalystin the form of the halide (e.g., as the chloride). This combined halogenmay be either fluorine, chlorine, iodine, bromine, or mixtures thereof.Of these, fluorine and, particularly, chlorine are preferred for thepurposes of the present invention. The halogen may be added to thecarrier material in any suitable manner, either during preparation ofthe support or before or after the addition of the other components. Forexample, the halogen may be added, at any stage of the preparation ofthe carrier material or to the calcined carrier material, as an aqueoussolution of a suitable decomposable halogen-containing compound such ashydrogen fluoride, hydrogen chloride, hydrogen bromide, ammoniumchloride, etc. The halogen component or a portion thereof, may becombined with the carrier material during the impregnation of the latterwith the platinum group, nickel, or uranium components; for example,through the utilization of a mixture of chloroplatinic acid and hydrogenchloride. In another situation, the alumina hydrosol which is typicallyutilized to form the preferred alumina carrier material may containhalogen and thus contribute at least a portion of the halogen componentto the final composite. For reforming, the halogen will be typicallycombined with the carrier material in an amount sufficient to result ina final composite that contains about 0.1 to about 3.5%, and preferablyabout 0.5 to about 1.5%, by weight of halogen, calculated on anelemental basis. In isomerization or hydrocracking embodiments, it isgenerally preferred to utilize relatively larger amounts of halogen inthe catalyst--typically, ranging up to about 10 wt. % halogen calculatedon an elemental basis, and more preferably, about 1 to about 5 wt. %. Itis to be understood that the specified level of halogen component in theinstant catalyst can be achieved or maintained during use in theconversion of hydrocarbons by continuously or periodically adding to thereaction zone a decomposable halogen-containing compound such as anorganic chloride (e.g. ethylene dichloride, carbon tetrachloride,t-butyl chloride) in an amount of about 1 to 100 wt. ppm. of thehydrocarbon feed, and preferably, about 1 to 10 wt. ppm.

Regarding especially preferred amounts of the various metalliccomponents of the subject catalyst, we have found it to be a goodpractice to specify the amounts of the nickel component and the uraniumcomponent as a function of the amount of the platinum group component.On this basis, the amount of the nickel component is ordinarily selectedso that the atomic ratio of nickel to platinum group metal contained inthe composite is about 0.1:1 to about 66:1, with the preferred rangebeing about 0.4:1 to about 18:1. Similarly, the amount of the uraniumcomponent is ordinarily selected to produce a composite containing anatomic ratio of uranium to platinum group metal of about 0.1:1 to about80:1, with the preferred range being about 0.5:1 to about 20:1.

Another significant parameter for the instant catalyst is the "totalmetals content" which is defined to be the sum of the platinum groupcomponent, the nickel component, and the uranium component, calculatedon an elemental basis. Good results are ordinarily obtained with thesubject catalyst when this parameter is fixed at a value of about 0.5 toabout 5 wt. %, with best results ordinarily achieved at a metals loadingof about 0.7 to about 4 wt. %.

In embodiments of the present invention wherein the instantmultimetallic catalytic composite is used for the dehydrogenation ofdehydrogenatable hydrocarbons or for the hydrogenation of hydrogenatablehydrocarbons, it is ordinarily a preferred practice to include an alkalior alkaline earth metal component in the composite and to minimize oreliminate the halogen component. More precisely, this optionalingredient is selected from the group consisting of the compounds of thealkali metals--cesium, rubidium, potassium, sodium, and lithium--and thecompounds of the alkaline earth metals--calcium, strontium, barium, andmagnesium. Generally, good results are obtained in these embodimentswhen this component constitutes about 0.1 to about 5 wt. % of thecomposite, calculated on an elemental basis. This optional alkali oralkaline earth metal component can be incorporated in the composite inany of the known ways, with impregnation with an aqueous solution of asuitable water-soluble, decomposable compound being preferred.

An optional ingredient for the multimetallic catalyst of the presentinvention is a Friedel-Crafts metal halide component. This ingredient isparticularly useful in hydrocarbon conversion embodiments of the presentinvention wherein it is preferred that the catalyst utilized has astrong acid or cracking function associated therewith--for example, anembodiment wherein hydrocarbons are to be hydrocracked or isomerizedwith the catalyst of the present invention. Suitable metal halides ofthe Friedel-Crafts type include aluminum chloride, aluminum bromide,ferric chloride, ferric bromide, zinc chloride, and the like compounds,with the aluminum halides and particularly aluminum chloride ordinarilyyielding best results. Generally, this optional ingredient can beincorporated into the composite of the present invention by any of theconventional methods for adding metallic halides of this type; however,best results are ordinarily obtained when the metallic halide issublimed onto the surface of the carrier material according to thepreferred method disclosed in U.S. Pat. No. 2,999,074. The component cangenerally be utilized in any amount which is catalytically effective,with a value selected from the range of about 1 to about 100 wt. % ofthe carrier material generally being preferred.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the final catalyst generallywill be dried at a temperature of about 200° to about 600° F. for aperiod of at least about 2 to about 24 hours or more, and finallycalcined or oxidized at a temperature of about 700° F. to about 1100° F.in an air to oxygen atmosphere for a period of about 0.5 to about 10hours in order to convert substantially all of the metallic componentsto the corresponding oxide form. Because a halogen component is utilizedin the catalyst, best results are generally obtained when the halogencontent of the catalyst is adjusted during the oxidation step byincluding a halogen or a halogen-containing compound such as HCl or anHCl-producing substance in the air or oxygen atmosphere utilized. Inparticular, when the halogen component of the catalyst is chlorine, itis preferred to use a mole ratio of H₂ O to HCl of about 5:1 to about100:1 during at least a portion of the oxidation step in order to adjustthe final chlorine content of the catalyst to a range of about 0.1 toabout 3.5 wt. %. Preferably, the duration of this halogenation step isabout 1 to 5 hours.

The resultant oxidized catalytic composite is preferably subjected to asubstantially water-free reduction step prior to its use in theconversion of hydrocarbons. This step is designed to selectively reducethe platinum group component to the elemental metallic state and toinsure a uniform and finely divided dispersion of the metalliccomponents throughout the carrier material, while maintaining theuranium component in a positive oxidation state. Preferably, asubstantially pure and dry hydrogen stream (i.e. less than 20 vol. ppm.H₂ O) is used as the reducing agent in this step. The reducing agent iscontacted with the oxidized catalyst at conditions including a reductiontemperature of about 800° F. to about 1200° F., preferably about 800° F.to about 1000° F., a gas hourly space velocity sufficient to rapidlydissipate any local concentrations of water formed during the reductionstep, and a period of time of about 0.5 to 10 hours effective to reducesubstantially all of the platinum group component to the elementalmetallic state while maintaining the uranium component in an oxidationstate above that of the elemental metal. If this reduction step isperformed with a hydrocarbon-free hydrogen stream at the temperatureindicated, and if the catalytically available nickel component isproperly distributed in the carrier material in the oxide form, asubstantial portion of the catalytically available nickel component maynot be reduced in this step. However, once the catalyst sees a flowingmixture of hydrogen and hydrocarbon (such as during the starting-up andlining-out of the hydrocarbon conversion process using same), at least amajor portion and, typically substantially all, of the catalyticallyavailable nickel component is quickly reduced at the specified reductiontemperature range. This reduction treatment may be performed in situ aspart of the start-up sequence if precautions are taken to predry theplant to a substantially water-free state and if substantiallywater-free hydrogen stream is used.

The resulting reduced catalytic composite is, in accordance with thebasic concept of the present invention, preferably maintained in asulfur-free state both during its preparation and thereafter during itsuse in the conversion of hydrocarbons. As indicated previously, thebeneficial interaction of the catalytically available nickel componentwith the other ingredients of the present catalytic composite iscontingent upon the maintenance of the nickel moiety in a highlydispersed, readily reducible state in the carrier material. Sulfur inthe form of sulfide adversely interferes with both the dispersion andreducibility of the catalytically available nickel component andconsequently it is a highly preferred practice to avoid presulfiding theselectively reduced acidic multimetallic catalyst resulting from thereduction step. Once the catalyst has been exposed to hydrocarbon for asufficient period of time to lay down a protective layer of carbon orcoke on the surface thereof, the sulfur sensitivity of the resultingcarbon-containing composite changes rather markedly and the presence ofsmall amounts of sulfur can be tolerated without permanently disablingthe catalyst. The exposure of the freshly reduced catalyst to sulfur canseriously damage the nickel component thereof and consequentlyjeopardize the superior performance characteristics associatedtherewith. However, once a protective layer of carbon is established onthe catalyst, the sulfur deactivation effect is less permanent andsulfur can be purged therefrom by exposure to a sulfur-free hydrogenstream at a temperature of about 800° to 1100° F.

According to the present invention, a hydrocarbon charge stock andhydrogen are contacted with the instant acidic multimetallic catalyst ina hydrocarbon conversion zone. This contacting may be accomplished byusing the catalyst in a fixed bed system, a moving bed system, afluidized bed system, or in a batch type operation, however, in view ofthe danger of attrition losses of the valuable catalyst and ofwell-known operational advantages, it is preferred to use either a fixedbed system or a dense-phase moving bed system such as is shown in U.S.Pat. No. 3,725,249. It is also contemplated that the contacting step canbe performed in the presence of a physical mixture of particles of thecatalyst of the present invention and particles of a conventionaldual-function catalyst of the prior art. In a fixed bed system, ahydrogen-rich gas and the charge stock are preheated by any suitableheating means to the desired reaction temperature and then are passedinto a conversion zone containing a fixed bed of the acidicmultimetallic catalyst. It is, of course, understood that the conversionzone may be one or more separate reactors with suitable meanstherebetween to insure that the desired conversion temperature ismaintained at the entrance to each reactor. It is also important to notethat the reactants may be contacted with the catalyst bed in eitherupward, downward, or radial flow fashion with the latter beingpreferred. In addition, the reactants may be in the liquid phase, amixed liquid-vapor phase, or a vapor phase when they contact thecatalyst, with best results obtained in the vapor phase.

In the case where the acidic multimetallic catalyst of the presentinvention is used in a reforming operation, the reforming system willtypically comprise a reforming zone containing one or more fixed beds ordense-phase moving beds of the catalysts. In a multiple bed system, itis, of course, within the scope of the present invention to use thepresent catalyst in less than all of the beds with a conventionaldual-function catalyst being used in the remainder of the beds. Thisreforming zone may be one or more separate reactors with suitableheating means therebetween to compensate for the endothermic nature ofthe reactions that take place in each catalyst bed. The hydrocarbon feedstream that is charged to this reforming system will comprisehydrocarbon fractions containing naphthenes and paraffins that boilwithin the gasoline range. The preferred charge stocks are thoseconsisting essentially of naphthenes and paraffins, although in somecases aromatics and/or olefins may also be present. This preferred classincludes straight run gasolines, natural gasolines, synthetic gasolines,partially reformed gasolines, and the like. On the other hand, it isfrequently advantageous to charge thermally or catalytically crackedgasolines or higher boiling fractions thereof. Mixtures of straight runand cracked gasolines can also be used to advantage. The gasoline chargestock may be a full boiling gasoline having an initial boiling point offrom about 50° to about 150° F. and an end boiling point within therange of from about 325° to about 425° F., or may be a selected fractionthereof which generally will be a higher boiling fraction commonlyreferred to as a heavy naphtha--for example, a naphtha boiling in therange of C₇ to 400° F. In some cases, it is also advantageous to chargepure hydrocarbons or mixtures of hydrocarbons that have been extractedfrom hydrocarbon distillates--for example, straight-chainparaffins--which are to be converted to aromatics. It is preferred thatthese charge stocks be treated by conventional catalytic pretreatmentmethods such as hydrorefining, hydrotreating, hydrodesulfurization,etc., to remove substantially all sulfurous, nitrogenous, andwater-yielding contaminants and to saturate any olefins that may becontained therein.

In other hydrocarbon conversion embodiments, the charge stock will be ofthe conventional type customarily used for the particular kind ofhydrocarbon conversion being effected. For example, in a typicalisomerization embodiment the charge stock can be a paraffinic stock richin C₄ to C₈ normal paraffins, or a normal butane-rich stock, or ann-hexane-rich stock, or a mixture of xylene isomers, or anolefin-containing stock, etc. In a dehydrogenation embodiment, thecharge stock can be any of the known dehydrogenatable hydrocarbons suchas an aliphatic compound containing 2 to 30 carbon atoms per molecule, aC₄ to C₃₀ normal paraffin, a C₈ to C₁₂ alkylaromatic, a naphthene, andthe like. In hydrocracking embodiments, the charge stock will betypically a gas oil, heavy cracked cycle oil, etc. In addition,alkylaromatics, olefins, and naphthenes can be conveniently isomerizedby using the catalyst of the present invention. Likewise, purehydrocarbons or substantially pure hydrocarbons can be converted to morevaluable products by using the acidic multimetallic catalyst of thepresent invention in any of the hydrocarbon conversion processes, knownto the art, that use a dual-function catalyst.

Since sulfur has a high affinity for nickel at hydrocarbon conversionconditions, best results are achieved in the conversion of hydrocarbonswith the instant acidic multimetallic catalytic composite when thecatalyst is used in a substantially sulfur-free environment. This isparticularly true in the catalytic reforming embodiment of the presentinvention. The expression "substantially sulfur-free environment" isintended to mean that the total amount (expressed as equivalentelemental sulfur) of sulfur or sulfur-containing compounds, which arecapable of producing a metallic sulfide at the reaction conditions used,entering the reaction zone containing the instant catalyst from anysource is continuously maintained at an amount equivalent to less than10 wt. ppm. of the hydrocarbon charge stock, more preferably less than 5wt. ppm., and most preferably less than 1 wt. ppm. Since in the ordinaryoperation of a conventional catalytic reforming process, whereininfluent hydrogen is autogenously produced, the prime source for anysulfur entering the reforming zone is the hydrocarbon charge stock,maintaining the charge stock substantially free of sulfur is ordinarilysufficient to ensure that the environment containing the catalyst ismaintained in the substantially sulfur-free state. More specifically,since hydrogen is a by-product of the catalytic reforming process,ordinarily the input hydrogen stream required for the process isobtained by recycling a portion of the hydrogen-rich stream recoveredfrom the effluent withdrawn from the reforming zone. In this typicalsituation, this recycle hydrogen stream will ordinarily be substantiallyfree of sulfur if the charge stock is maintained free of sulfur. Ifautogenous hydrogen is not utilized, then, of course, the concept of thepresent invention requires that the input hydrogen stream be maintainedsubstantially sulfur-free; that is, less than 10 vol. ppm. of H₂ S,preferably less than 5 vol. ppm., and most preferably less than 1 vol.ppm.

The only other possible sources of sulfur that could interfere with theperformance of the instant catalyst are sulfur that is initiallycombined with the catalyst and/or with the plant hardware. As indicatedhereinbefore, a highly preferred feature of the present acidicmultimetallic catalyst is that it is maintained in a substantiallysulfur-free state; therefore, sulfur released from the catalyst is notusually a problem in the present process. Hardware sulfur is ordinarilynot present in a new plant; it only becomes a problem when the presentprocess is to be implemented in a plant that has seen service with asulfur-containing feedstream. In this latter case, the preferredpractice of the present invention involves an initial pretreatment ofthe sulfur-containing plant in order to remove substantially all of thedecomposable hardware sulfur therefrom. This can be easily accomplishedby any of the techniques for stripping sulfur from hardware known tothose in the art; for example, by the circulation of a substantiallysulfur-free hydrogen stream through the internals of the plant at arelatively high temperature of about 800° to about 1200° F. until the H₂S content of the effluent gas stream drops to a relatively lowlevel--typically, less than 5 vol. ppm. and preferably less than 2 vol.ppm. In sum, the preferred sulfur-free feature of the present inventionrequires that the total amount of detrimental sulfur entering thehydrocarbon conversion zone containing the hereinbefore described acidicmultimetallic catalyst must be continuously maintained at asubstantially low level; specifically, the total amount of sulfur mustbe held to a level equivalent to less than 10 wt. ppm., and preferablyless than 1 wt. ppm., of the feed.

In the case where the sulfur content of the feed stream for the presentprocess is greater than the amounts previously specified, it is, ofcourse, necessary to treat the charge stock in order to remove theundesired sulfur contaminants therefrom. This is easily accomplished byusing any one of the conventional catalytic pretreatment methods such ashydrorefining, hydrotreating, hydrodesulfurization, and the like toremove substantially all sulfurous, nitrogenous, and water-yieldingcontaminants from this freestream. Ordinarily, this involves subjectingthe sulfur-containing feedstream to contact with a suitablesulfur-resistant hydrorefining catalyst in the presence of hydrogenunder conversion conditions selected to decompose sulfur contaminantscontained therein and form hydrogen sulfide. The hydrorefining catalysttypically comprises one or more of the oxides or sulfides of thetransition metals of Groups VI and VIII of the Periodic Table. Aparticularly preferred hydrorefining catalyst comprises a combination ofa metallic component from the iron group metals of Group VIII and of ametallic component of the Group VI transition metals combined with asuitable porous refractory support. Particularly good results have beenobtained when the iron group component is cobalt and/or nickel and theGroup VI transition metal is molybdenum or tungsten. The preferredsupport for this type of catalyst is a refractory inorganic oxide of thetype previously mentioned. For example, good results are obtained with ahydrorefining catalyst comprising cobalt oxide and molybdenum oxidesupported on a carrier material comprising alumina and silica. Theconditions utilized in this hydrorefining step are ordinarily selectedfrom the following ranges: a temperature of about 600° to about 950° F.,a pressure of about 500 to about 5000 psig., a liquid hourly spacevelocity of about 1 to about 20 hr.⁻¹, and a hydrogen circulation rateof about 500 to about 10,000 standard cubic feet of hydrogen per barrelof charge. After this hydrorefining step, the hydrogen sulfide, ammonia,and water liberated therein, are then easily removed from the resultingpurified charge stock by conventional means such as a suitable strippingoperation. Specific hydrorefining conditions are selected from theranges given above as a function of the amounts and kinds of the sulfurcontaminants in the feedstream in order to produce a substantiallysulfur-free charge stock which is then charged to the process of thepresent invention.

In a reforming embodiment, it is generally preferred to utilize thenovel acidic multimetallic catalytic composite in a substantiallywater-free environment. Essential to the achievement of this conditionin the reforming zone is the control of the water level present in thecharge stock and the hydrogen stream which are charged to the zone. Bestresults are ordinarily obtained when the total amount of water enteringthe conversion zone from any source is held to a level less than 20 ppm.and preferably less than 5 ppm. expressed as weight of equivalent waterin the charge stock. In general, this can be accomplished by carefulcontrol of the water present in the charge stock and in the hydrogenstream. The charge stock can be dried by using any suitable drying meansknown to the art, such as a conventional solid adsorbent having a highselectivity for water, for instance, dehydrated sodium or calciumzeolitic crystalline aluminosilicates, silica gel, activated alumina,molecular sieves, anhydrous calcium sulfate, high surface area sodium,and the like adsorbents. Similarly, the water content of the chargestock may be adjusted by suitable stripping operations in afractionation column or like device. And in some cases, a combination ofadsorbent drying and distillation drying may be used advantageously toeffect almost complete removal of water from the charge stock. In anespecially preferred mode of operation, the charge stock is dried to alevel corresponding to less than 5 wt. ppm. of H₂ O equivalent. Ingeneral, it is preferred to maintain the hydrogen stream entering thehydrocarbon conversion zone at a level of about 10 vol. ppm. of water orless and most preferably about 5 vol. ppm. or less. If the water levelin the hydrogen stream is too high, drying of same can be convenientlyaccomplished by contacting the hydrogen stream with a suitable desiccantsuch as those mentioned above.

In the reforming embodiment, an effluent stream is withdrawn from thereforming zone and passed through a cooling means to a separation zone,typically maintained at about 25° to 150° F., wherein a hydrogen-richgas stream is separaed from a high octane liquid product stream,commonly called an unstabilized reformate. When the water level in thehydrogen stream is outside the range previously specified, at least aportion of this hydrogen-rich gas stream is withdrawn from theseparating zone and passed through an adsorption zone containing anadsorbent selective for water. The resultant substantially water-freehydrogen stream can then be recycled through suitable compressing meansback to the reforming zone. The liquid phase from the separating zone istypically withdrawn and commonly treated in a fractionating system inorder to adjust the butane concentration, thereby controlling front-endvolatility of the resulting reformate.

The operating conditions utilized in the numerous hydrocarbon conversionembodiments of the present invention are in general those customarilyused in the art for the particular reaction, or combination ofreactions, that is to be effected. For instance, alkylaromatic, olefin,and paraffin isomerization conditions include: a temperature of about32° F. to about 1000° F. and preferably from about 75° to about 600° F.;a pressure of atmospheric to about 100 atmospheres; a hydrogen tohydrocarbon mole ratio of about 0.5:1 to about 20:1, and an LHSV(calculated on the basis of equivalent liquid volume of the charge stockcontacted with the catalyst per hour divided by the volume of conversionzone containing catalyst) of about 0.2 hr.⁻¹ to 10 hr.⁻¹.Dehydrogenation conditions include: a temperature of about 700° to about1250° F., a pressure of about 0.1 to about 10 atmospheres, a liquidhourly space velocity of about 1 to 40 hr.⁻¹, and a hydrogen tohydrocarbon mole ratio of about 1:1 to 20:1. Likewise, typicallyhydrocracking conditions include: a pressure of about 500 psig. to about3000 psig., a temperature of about 400° F. to about 900° F., an LHSV ofabout 0.1 hr.⁻¹ to about 10 hr.⁻¹, and hydrogen circulation rates ofabout 1000 to 10,000 SCF per barrel of charge.

In the reforming embodiment of the present invention, the pressureutilized is selected from the range of about 0 psig. to about 1000psig., with the preferred pressure being about 50 psig. to about 600psig. Particularly good results are obtained at low or moderatepressure; namely, a pressure of about 100 to 450 psig. In fact, it is asingular advantage of the present invention that it allows stableoperation at lower pressure than have heretofore been successfullyutilized in so-called "continuous" reforming systems (i.e. reforming forperiods of about 15 to about 200 or more barrels of charge per pound ofcatalyst without regeneration) with all platinum monometallic catalyst.In other words, the acidic multimetallic catalyst of the presentinvention allows the operation of a continuous reforming system to beconducted at lower pressure (i.e. 100 to about 350 psig) for about thesame or better catalyst cycle life before regeneration as has beenheretofore realized with conventional monometallic catalysts at higherpressure (i.e. 400 to 600 psig). On the other hand, the extraordinaryactivity and activity-stability characteristics of the catalyst of thepresent invention enables reforming conditions conducted at pressures of400 to 600 psig. to achieve substantially increased catalyst cycle lifebefore regeneration.

The temperature required for reforming with the instant catalyst ismarkedly lower than that required for a similar reforming operationusing a high quality catalyst of the prior art. This significant anddesirable feature of the present invention is a consequence of theextraordinary activity of the acidic multimetallic catalyst of thepresent invention for the octane-upgrading reactions that are preferablyinduced in a typical reforming operation. Hence, the present inventionrequires a temperature in the range of from about 800° F. to about 1100°F. and preferably about 900° F. to about 1050° F. As is well known tothose skilled in the continuous reforming art, the initial selection ofthe temperature within this broad range is made primarily as a functionof the desired octane of the product reformate considering thecharacteristics of the charge stock and of the catalyst. Ordinarily, thetemperature then is thereafter slowly increased during the run tocompensate for the inevitable deactivation that occurs to provide aconstant octane product. Therefore, it is a feature of the presentinvention that not only is the initial temperature requirementsubstantially lower, but also the rate at which the temperature isincreased in order to maintain a constant octane product issubstantially lower for the catalyst of the present invention than foran equivalent operation with a high quality reforming catalyst which ismanufactured in exactly the same manner as the catalyst of the presentinvention except for the inclusion of the nickel and uranium components.Moreover, for the catalyst of the present invention, the C₅ + yield lossfor a given temperature increase is substantially lower than for a highquality reforming catalyst of the prior art. The extraordinary activityof the instant catalyst can be utilized in a number of highly beneficialways to enable increased performance of a catalytic reforming processrelative to that obtained in a similar operation with a monometallic orbimetallic catalyst of the prior art, some of these are: (1) Octanenumber of C₅ 30 product can be substantially increased withoutsacrificing catalyst run length. (2) The duration of the processoperation (i.e. catalyst run length or cycle life) before regenerationbecomes necessary can be significantly increased. (3) C₅ + yield can beincreased by lowering average reactor pressure with no change incatalyst run length. (4) Investment costs can be lowered without anysacrifice in cycle life by lowering recycle gas requirements therebysaving on capital cost for compressor capacity or by lowering initialcatalyst loading requirements thereby saving on cost of catalyst and oncapital cost of the reactors. (5) Throughput can be increased sharply atno sacrifice in catalyst cycle life if sufficient heater capacity isavailable.

The reforming embodiment of the present invention also typicallyutilizes sufficient hydrogen to provide an amount of about 1 to about 20moles of hydrogen per mole of hydrocarbon entering the reforming zone,with excellent results being obtained when about 2 to about 6 moles ofhydrogen are used per mole of hydrocarbon. Likewise, the liquid hourlyspace velocity (LHSV) used in reforming is selected from the range ofabout 0.1 to about 10 hr.⁻¹, with a value in the range of about 1 toabout 5 hr.⁻¹ being preferred. In fact, it is a feature of the presentinvention that it allows operations to be conducted at higher LHSV thannormally can be stably achieved in a continuous reforming process with ahigh quality reforming catalyst of the prior art. This last feature isof immense economic significance because it allows a continuousreforming process to operate at the same throughput level with lesscatalyst inventory or at greatly increased throughput level with thesame catalyst inventory than that heretofore used with conventionalreforming catalyst at no sacrifice in catalyst life before regeneration.

The following working examples are given to illustrate further thepreparation of the preferred acidic substantially sulfur-freemultimetallic catalytic composite of the present invention and the usethereof in the conversion of hydrocarbons. It is understood that theexamples are intended to be illustrative rather than restrictive.

EXAMPLE I

A sulfur-free alumina carrier material comprising 1/16 inch spheres isprepared by: forming an aluminum hydroxyl chloride sol by dissolvingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding hexamethylenetetramine to the resulting sol, gelling theresulting solution by dropping it into an oil bath to form sphericalparticles of an alumina hydrogel, aging and washing the resultingparticles, and finally drying and calcining the aged and washedparticles to form spherical particles of gamma-alumina containing about0.3 wt. % combined chloride. Additional details as to this method ofpreparing the preferred carrier material are given in the teachings ofU.S. Pat. No. 2,620,314.

An aqueous acidic sulfur-free impregnation solution containingchloroplatinic acid, nickel chloride, uranyl acetate and hydrogenchloride is then prepared. The alumina carrier material is thereafteradmixed with the impregnation solution. The amounts of metal reagentscontained in this impregnation solution is calculated to result in afinal composite containing, on an elemental basis, 0.3 wt. % platinum,1.0 wt. % uranium, and 1.0 wt. % nickel. In order to insure uniformdispersion of the metallic components throughout the carrier material,the amount of hydrochloric acid used is about 3 wt. % of the aluminaparticles. This impregnation step is performed by adding the carriermaterial particles to the impregnation mixture with constant agitation.In addition, the volume of the solution is approximately the same as thebulk volume of the carrier material particles. The impregnation mixtureis maintained in contact with the carrier material particles for aperiod of about 1/2 to about 3 hours at a temperature of about 70° F.Thereafter, the temperature of the impregnation mixture is raised toabout 225° F. and the excess solution was evaporated in a period ofabout 1 hour. The resulting dried impregnated particles are thensubjected to an oxidation treatment in a sulfur-free dry air stream at atemperature of about 930° F. and a GHSV of about 500 hr.⁻¹ for about 1/2hour. This oxidation step is designed to convert substantially all ofthe metallic ingredients to the corresponding oxide forms. The resultingoxidized spheres are subsequently contacted in a halogen-treating stepwith a sulfur-free air stream containing H₂ O and HCl in a mole ratio ofabout 30:1 for about 2 hours at 930° F. and a GHSV of about 500 hr.⁻¹ inorder to adjust the halogen content of the catalyst particles to a valueof about 1 wt. %. The halogen-treated spheres are thereafter subjectedto a second oxidation step with a dry sulfur-free air stream at 930° F.and a GHSV of 500 hr.⁻¹ for an additional period of about 1/2 hour.

The oxidized and halogen-treated catalyst particles are then subjectedto a dry prereduction treatment, designed to reduce substantially all ofthe platinum component to the elemental metallic state while maintainingthe uranium component in a positive oxidation state, by contacting themfor about 1 hour with a substantially hydrocarbon-free and sulfur-freehydrogen stream containing less than 5 vol. ppm. H₂ O at a temperatureof about 930° F., a pressure slightly above atmospheric, and a flow rateof the hydrogen stream through the catalyst particles corresponding to aGHSV of about 400 hr.⁻¹.

A sample of the resulting reduced catalyst particles is analyzed andfound to contain, on an elemental basis, about 0.3 wt. % platinum, about1.0 wt. % nickel, about 1.0 wt. % uranium, and about 1 wt. % chloride.This corresponds to an atomic ratio of uranium to platinum of 2.7:1 andto an atomic ratio of nickel to platinum of 11:1.

EXAMPLE II

A portion of the spherical acidic sulfur-free multimetallic catalystparticles produced by the method described in Example I is loaded into ascale model of a continuous, fixed bed reforming plant of conventionaldesign. In this plant a heavy Kuwait naphtha and hydrogen arecontinuously contacted at reforming conditions: a liquid hourly spacevelocity of 3.0 hr.⁻¹, a pressure of 300 psig., a hydrogen-containingrecycle gas to hydrocarbon mole ratio of 5:1, and a temperaturesufficient to continuously produce a C₅ + reformate of 100 F-1 clear. Itis to be noted that these are exceptionally severe conditions.

The heavy Kuwait naphtha has an API gravity at 60° F. of 60.4, aninitial boiling point of 184° F., a 50% boiling point of 256° F., and anend boiling point of 360° F. In addition, it contains about 8 vol. %aromatics, 71 vol. % paraffins, 21 vol. % naphthenes, 0.5 weight partsper million sulfur, and 5 to 8 weight parts per million water. The F-1clear octane number of the raw stock is 40.0.

The fixed bed reforming plant is made up of a reactor containing theacidic, sulfur-free multimetallic catalyst, a hydrogen separation zone,a debutanizer column, and suitable heating, pumping, cooling, andcontrolling means. In this plant, a hydrogen recycle stream and thecharge stock are commingled and heated to the desired temperature. Theresultant mixture is then passed downflow into a reactor containing thecatalyst as a fixed bed. An effluent stream is then withdrawn from thebottom of the reactor, cooled to about 55° F. and passed to a separatingzone wherein a hydrogen-rich and methane-rich gaseous phase separatesfrom a liquid hydrocarbon phase. A portion of the gaseous phase iscontinuously passed through a high surface sodium scrubber and theresulting water-free hydrogen-containing stream recycled to the reactorin order to supply hydrogen thereto, and the excess gaseous phase overthat needed for plant pressure is recovered as excess separator gas. Theliquid hydrocarbon phase from the hydrogen separating zone is withdrawntherefrom and passed to a debutanizer column of conventional designwherein light ends are taken overhead as debutanizer gas and a C₅ +reformate stream recovered as bottoms.

The test run is continued for a catalyst life of about 10 barrels ofcharge per pound of catalyst utilized, and it is determined that theactivity, selectivity, and stability characteristics of the presentmultimetallic catalyst are vastly superior to those observed in asimilar type test with a conventional all platinum commercial reformingcatalyst. More specifically, the results obtained from the subjectcatalyst are superior to the platinum metal-containing catalyst of theprior art in the area of initial and average temperature required tomake octane, average level of debutanizer gas production, average C₅ +yield at octane, average rate of temperature increase necessary tomaintain octane and C₅ + yield decline rate.

It is intended to cover by the following claims, all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the catalystformulation art or the hydrocarbon conversion art.

We claim as our invention:
 1. An acidic catalytic composite comprising a porous carrier material containing, on an elemental basis, about 0.01 to about 2 wt. % platinum group metal, about 0.05 to about 5 wt. % nickel, about 0.1 to about 10 wt. % uranium, and about 0.1 to about 3.5 wt. % halogen; wherein the platinum group, catalytically available nickel, and uranium components are uniformly dispersed throughout the porous carrier material; wherein substantially all of the platinum group component is present in the elemental metallic state; wherein substantially all of the uranium component is present in an oxidation state above that of the elemental metal; and wherein substantially all of the catalytically available nickel component is present in the elemental metallic state or in a state which is reducible to the elemental metallic state, or in a mixture of these states.
 2. An acidic catalytic composite as defined in claim 1 wherein the platinum group component is platinum.
 3. An acidic catalytic composite as defined in claim 1 wherein the platinum group component is iridium.
 4. An acidic catalytic composite as defined in claim 1 wherein the platinum group component is rhodium.
 5. An acidic catalytic composite as defined in claim 1 wherein the platinum group component is palladium.
 6. An acidic catalytic composite as defined in claim 1 wherein the porous carrier material is a refractory inorganic oxide.
 7. An acidic catalytic composite as defined in claim 6 wherein the refractory inorganic oxide is alumina.
 8. An acidic catalytic composite as defined in claim 1 wherein the halogen component is combined chlorine.
 9. An acidic catalytic composite as defined in claim 1 wherein the atomic ratio of uranium to platinum group metal is about 0.1:1 to about 80:1 and wherein the atomic ratio of nickel to platinum group metal is about 0.1:1 to about 66:1.
 10. An acidic catalytic composite as defined in claim 1 wherein substantially all of the uranium component is present in the form of uranium oxide or uranium oxyhalide or uranium aluminate or mixtures thereof.
 11. An acidic catalytic composite as defined in claim 1 wherein the composite contains about 0.05 to about 1 wt. % platinum group metal, about 0.1 to about 2.5 wt. % nickel, about 0.25 to about 5 wt. % uranium, and about 0.5 to about 1.5 wt. % halogen.
 12. An acidic catalytic composite as defined in claim 1 wherein the catalytic composite is in substantially a sulfur-free state. 